JPS6159325A - Lighting device of copying machine or the like - Google Patents

Abstract

PURPOSE:To prevent a decrease in lighting efficiency by bearing relations, i.e. theta=90 deg.-alpha and 60 deg.>alpha>45 deg. between the angle of incident of parallel luminous flux to extremely small reflecting surfaces of the lowermost stage of a Fresnel reflecting mirror and the angle theta between the parallel luminous flux and reflecting mirror. CONSTITUTION:Light from a spot light source 1 is made by a parabolic reflecting mirror 2 into parallel luminous flux 3, which is converged linearly on an original through the Fresnel reflecting mirror 4. In this case, theta=90 deg.-alpha and 60 deg.>alpha>45 deg.. Consequently, none of joint parts of extremely small reflecting surfaces of the lowermost stage cuts off reflected light, and the lighting effi ciency is prevented from decreasing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an illumination device for a copying machine or the like that illuminates a document to be copied while scanning it.

2. Description of the Related Art A scanning illumination device used in a conventional copying machine illuminates a document by moving a light source along the document to be copied. However, with this method, the life of the light source is short, as the lamp used for the light source is easily burnt out due to vibration or shock during movement, and the light source moves directly under the document table, so copies are made with the document table cover open. In this case, the light directly entered the eyes of the workers, creating a very dazzling problem.

To improve the above-mentioned defects, there are methods described in Japanese Patent Publication No. 53-41976 shown in Figure 4, and those shown in Figures 5 and 6.
The method described in Japanese Unexamined Patent Application Publication No. 113166/1983 as shown in the figure has been proposed.

In the above examples, a light beam emitted from a point light source α is converted into a parallel light beam using a reflex reflector b or a collimator lens c, and this light beam is condensed linearly onto one side of the original by a parabolic reflector d or a curved reflector. It is something.

Problems to be Solved by the Invention However, in the above-mentioned conventional illumination device, the optical system that produces parallel light beams and the optical system that condenses the parallel light beams are both curved shapes or thick lenses, making adjustment difficult. In addition to requiring a lot of work, the curved reflector in particular uses glass cord material with high surface precision, and is also heavy. Therefore, it is necessary to support the curved reflector without generating scanning dark vibrations, and there is a problem that the supporting means is complicated and expensive.

In order to improve this problem, there is a method of using a linear condensing Fresnel reflector 1 as shown in FIG. If they are set up, good light condensation can be achieved in region A, but in region B, where the incident angle α to the micro-reflective surface i exceeds 90°-〇, the joint portion of the micro-reflective surface i traces the reflected light. Therefore, the parallel light beam shown by the thick line in Fig. 8 is
There was a problem with poor lighting efficiency as the light was not focused. Therefore, by using only area A, which has good lighting efficiency,
It is also possible to condense the light as shown in the figure, but even in this case, if θ is set to 45° or more, the document k will be illuminated in one direction, causing a problem that a shadow will appear at the edge of the document.

This invention was made for the purpose of improving the above-mentioned problems.

A flat Fresnel reflector is used as a means for solving the problem and a means for linearly converging a parallel light beam onto a document, and the flat Fresnel reflector is used to adjust the angle of incidence of the parallel light beam on a minute reflective surface to α. , when the angle between the parallel light beam and the flat Fresnel reflector is θ, θ=906−α
, 60°>α>45°, thereby preventing a decrease in lighting efficiency.

Embodiment An embodiment of the present invention will be described in detail with reference to the drawings. In the figure, 1 is a point light source such as a small four-gen lamp, and 2 is a parabolic reflector that collimates the light beam emitted from the point light source 1 into a parallel light beam. The parallel light beam 3 collimated by the parabolic reflecting mirror 2 is linearly condensed by a flat Fresnel reflecting mirror 4 onto an original 6 placed on an original platen 5.

The above-mentioned flat plate reflecting mirror 4 has an angle α at which the lowest parallel light beam 31 enters the minute reflection plane, and when θ is the angle between the above light beam 3' and the flat Fresnel reflecting mirror 40, θ=90°−α α〉 The angle is set to 45°.

Also, the length l of the flat Fresnel reflector 4 is ''' / cot d (d '', the width of the luminous flux), and as α increases, the length 2 also increases, but the length l
If Z is too large, it will be inconvenient to mount it for scanning, so Z (about 2d is recommended)
° was taken as the upper limit of α.

In the above configuration, a small Iffgen lamp is used as a point light source 1, collimated into a parallel beam 3 by a parabolic reflector 2, and a flat Fresnel reflector set at α=57.5° and θ=32.5°. 4, the light was focused linearly onto the document 6 on the document table 5. Further, the pitch of the minute reflection planes of the flat Fresnel reflecting mirror 4 was set to Q, 5 mm.

As a result, the illuminance distribution shown in FIG. 2(a) was obtained on the light condensing surface of the original 6. This figure shows that the left and right sides are evenly illuminated.

By the way, under the same conditions, the flat Fresnel reflector y shown in Figure 8
The illuminance distribution in the case of using the light beam is as shown in FIG.

On the other hand, FIG. 3 shows another embodiment in which the flat Fresnel reflector 4 is miniaturized, and the lower half of the flat Fresnel reflector 4 (C
(area) and the upper portion (area D) have different shapes. In other words, α in region C. = 57°, winter = 33°
In region D, to = 45°, θ. Even if it is set so that = 45°, this causes flat Fresnel reflection! The length 2 of 4 can be made smaller than that of the previous embodiment, making it easy to mount it so that it can be scanned freely.

Effects of the Invention As described in detail above, the present invention uses a flat Fresnel reflector as a means for linearly converging a parallel light beam onto a document, and uses the flat Fresnel reflector to focus the parallel light beam on a minute reflective surface. When the angle is α and the angle between the parallel light beam and the flat Fresnel reflection shell is θ, θ=90°−α, 60°〉α〉45°
Since it is installed so that there is almost no decrease in illumination efficiency and there is no unidirectional illumination, it is possible to eliminate problems such as shadows occurring at the edges of the document.

Furthermore, by employing a flat Fresnel reflector, the reflector can be made smaller and lighter than conventional reflectors, which also has the effect of facilitating support means against vibrations during scanning.

[Brief explanation of the drawing]

Figure 1 shows one embodiment of the present invention, Figure 1 is a side view, Figure 2 is a diagram showing illuminance distribution, Figure 3 is an explanatory diagram showing another embodiment, and Figures 4 to 4 are diagrams showing an illuminance distribution. FIG. 9 is a conventional explanatory diagram. 1 is a point light source, 4 is a flat Fresnel reflector, and 6 is a manuscript. Judo Kaishin Ward Ward Dimensions D 綜沫 6th figure 8th figure 9th figure

Claims (1)

[Claims] In the device that illuminates the original 6 by converting the luminous flux emitted from the point light source 1 into a parallel luminous flux and condensing it linearly onto the original 6 by a reflecting means, the parallel luminous flux is focused onto the original 6 in a linear manner. A flat Fresnel reflecting mirror 4 is used as a means for
When the incident angle of
A lighting device for a copying machine, etc. that is installed so that the angle of